A new research suggests that an unusual Greek coin, minted around 120 BC, may have marked a rare astronomical event – when Jupiter was eclipsed by the Moon.

It happened on January 17, 121 BC and was visible in Antioch, the capital of the Seleucid Empire.

The coin had a portrait of Antiochos VIII, the king who minted it, on one side and god Zeus with a crescent moon above his head and a star-like object (may be Jupiter) hovering above the palm of his right hand on the other side, reports Unreported Heritage News.

“Nobody ever re-used this iconography again – it was a one off,” said Professor Robert Weir of the University of Windsor in Canada.

Antiochos VIII was the ruler of the Seleucid Empire, a kingdom created by one of Alexander the Great’s officers, after the great conqueror died in 323 BC.

Weir, who was interested in astronomy and ancient coins, was curious why Antiochos would mint a piece of currency with such an unusual drawing – could there have been something going on in the night sky?

He found that on January 17, 121 BC, the city’s residents would have seen Jupiter blocked out by the moon, an event modern day astronomers call an ‘occultation’.

Also “Jupiter, when it was eclipsed by the moon, was in the constellation of Cancer, which is a very significant constellation,” he said.

“This means that there might be a great king coming, or being born – in yria, because Cancer governs that part of the world the ancient astrologers believed,” he added.

That wasn’t all that was going on in the night sky.

“I noticed that there were other favourable occultations happening at the same time. There was another occultation of Jupiter within the year and just a week after the first one there was an occultation of Venus which is also a very good omen,” he said.

Antiochos VIII, a king ruling a shrinking empire alongside his murderous mother, may have felt that the heavens were finally with him.

“It was significant in a good way – an occultation of Jupiter has to do with omens for kings,” said Weir.

But unfortunately for Antiochos, his empire would endure conflict, with one of his brothers, Antiochos IX, disputing his right to the throne.

Eventually the two had to agree to divide what was left of the Seleucid kingdom.

In the meantime, the king’s run of cosmic good luck had come to an end.

Weir said that ‘a few years after he killed his mom there were (all) sorts of really bad luck eclipses of Mars and Saturn’.

Even worse, shortly before the coin stopped being minted, around 114 BC, ‘something happened in the heavens that happens only once every 2,000 years or so,’ he said.

“The moon eclipsed Mars and Saturn at the very same time. An event that’s about the worst omen you can get,” he said.

The study was presented at the recent annual meeting of the Archaeological Institute of America.